"Open the book to page ninety-nine and read, and the quality of the whole will be revealed to you."
--Ford Madox Ford

Wednesday, November 7, 2012

Mike Goldsmith's "Discord: The Story of Noise"

Mike Goldsmith is the former Head of the Acoustic Group at the United Kingdom's National Physical Laboratory and an author of many books for general readers. Two of his books have been short-listed for the Aventis prize (now the Royal Society prize) for science books.

One of the things I love about the subject of noise.... no, really, there is lots to love... is that it is full of mysteries, from the sources of strange undersea sounds to the mechanism by which some meteors can be heard long before sound waves have time to get from them to the hearer. And page 99 is about one of these: the Railway Bonus. The Bonus is a mark of the strange affection that humans have for the sounds of trains: many experiments and surveys over many decades have established that listeners are significantly less annoyed by railway noise than they are by that made by other traffic. So well-accepted is this that planners knock 5 or even 10 dB off their noise predictions if the noise source is a railway train.

In writing Discord: The Story of Noise I learned many things, and one of them is the antonym for bonus: "malus". And the reason I learned it is that the Railway Bonus has a sinister relative: the Aircraft Malus. If the Bonus is a blessing for railways companies, the Malus is a curse for aerospace agencies, and it means that people are as annoyed by an aircraft flying over as they are by a car driving past whose sound output is objectively about 5 dB more intense.

For some time, the supposed explanation for this referred to the "flying over" element. Of course, experts said, a large object thundering by above your head is bound to generate at least a fleeting fear that it might stop flying and start falling. Or maybe not, they added in 2005, when experiments showed that aircraft noise from above is less annoying that aircraft noise from other directions.